hsm: remove master info from getStorageDomainInfo

The pool metadata doesn't belong in the storage domain information
and ovirt-engine never read those values.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1033942
Change-Id: I8c046db3884b56b57cc1bf040f3e9cc136c6d877
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/22824
Reviewed-by: Ayal Baron <abaron@redhat.com>
Reviewed-by: Saggi Mizrahi <smizrahi@redhat.com>